started unlearning setup

Data.py

@@ -80,6 +80,10 @@ def select_top_ids(dataset, class_size):
 
 # split class images to train and test set.
 def get_indices(dataset, identities, split_at, size = 30):
+
+    if split_at >= size: # debug safety
+        raise ValueError(f"Split point ({split_at}) must be less than total size ({size}).")
+    
     train_indices = []
     test_indices = []